ICA 1 CH 26 CONSERVATION BIOLOGY GROUP # (NAME) _____________________
Names__________________ ____________________________ ________________________
1. Small populations can go into an ever-descending spiral in population size leading to their
eventual extinction. Sometimes their demise is driven by their genetics. Put the list of italicized
words into the correct boxes in the concept map. On the arrows, add a + or – to indicate whether
the process contributes positive feedback, thereby adding to the population decline.
inbreeding
lower reproduction
reduction in fitness
random genetic drift
higher mortality
loss of genetic
variability
higher
mortality
small
population size
random genetic
drift
inbreeding
lower
reproduction
loss of genetic
variability
reduction in
fitness
2. The probability of stochastic extinction:
A. increases or decreases over time? increases
B. increases or decreases as a function of population size
3. Bighorn Sheep Table
In one concise sentence summarize two major points illustrated.
% of population persisting increases as population size increases,
4. Elephant Table
A. State the main result (= describe pattern) for:
1. population of 3000 (in 2500 km2):
Cumulative probability of extinction increases to about .4% over 1000 years
2. population of 300 (in 250 km2):
Cumulative probability of extinction increases to about 20% over 1000 years
B. Summarize in one concise sentence the main ‘take home’ message.
As population size decreases, the cumulative probability of extinction increases to
near certainty over 1000 years.
5. Scandanavian wolf population
A. Develop a hypothesis that leads logically to the stated prediction below.
If…the small population is highly inbred and has low genetic variation,
then the size of a small population will increase sharply when a new male arrives.
B. Summarize the effect of inbreeding on wolf pup survival.
As the inbreeding coefficient increases, the probability of winter survival decreases.
6. Table 1 # alleles retained
A. Summarize column 2: More alleles are lost in populations of small size than large size.
B. What is the second key ‘take home’ point that is made by the contrasting data in column 3?
Alleles with a low frequency in the original population tend to be lost more easily in small
populations than alleles with high frequency.
7. Table 2. Summarize how the size of the founding population affects genetic variation.
A higher % of original heterozygosity is lost with populations founded by few than many
individuals.
8. Table 3.
A. What is the overarching general conclusion?
Small populations of constant size always lose heterozygosity through time.
B. How is that conclusion further qualified by looking at differences between populations
of 100 vs 2?
The smaller the population is, the more rapidly heterozygosity is lost.
C. How is that conclusion further qualified by looking at differences among columns of
a given row?
The higher the number of generations a population of small size is bred, the more
heterozygosity is lost.